Sizing a dehumitifer
#9
How do I size a dehumidifier?  My shop is in the garage.  It is warmer and rainy today.  I could feel the moisture on the equipment.  I have a 30 pint dehumidifier I brought with me, from when I lived in an apartment.  I took it out to the garage this evening.  It is telling me the air is at 95% humidity. 

A Google search is indicating a 30 pint dehumidifier will cover 1500 square feet.  I am not convinced that is true in the garage.  My garage is only about 1000 square feet, but there is a LOT of moisture, at least in the spring and fall.

Does anyone here have any expertise in this area.
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#10
Short of having a bunch more info like air infiltration rates, it can't be calculated. Is it 30 pints a day, week, month or is that the reservoir size?  Take what you have and run it for a couple days, see what it does.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#11
(02-19-2018, 09:27 PM)blackhat Wrote: Short of having a bunch more info like air infiltration rates, it can't be calculated. Is it 30 pints a day, week, month or is that the reservoir size?  Take what you have and run it for a couple days, see what it does.

Dehumidifiers are rated at max pints removal capacity per 24 hours. 

To your point, I will have a better idea in the morning.
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#12
I know how they are supposed to be sized. I give those labels as much credence as the hp ratings on shop vacs.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#13
(02-19-2018, 08:43 PM)Cecil Wrote: How do I size a dehumidifier?  My shop is in the garage.  It is warmer and rainy today.  I could feel the moisture on the equipment.  I have a 30 pint dehumidifier I brought with me, from when I lived in an apartment.  I took it out to the garage this evening.  It is telling me the air is at 95% humidity. 

A Google search is indicating a 30 pint dehumidifier will cover 1500 square feet.  I am not convinced that is true in the garage.  My garage is only about 1000 square feet, but there is a LOT of moisture, at least in the spring and fall.

Does anyone here have any expertise in this area.

Run your dehumidifier for 24 hours and collect the water. Then you will have a true reading of it's efficiency. Check your humidity at that point. I have a Sante Fe Advance 2 that is rated at 90 pints/24 hours and it easily meets that 90 pints. It keeps my encapsulated crawl space at 45% without running a lot. But it is a fairly large, high-end model ($1400). 

But some cheaper models extract water fairly well, but run a lot more and are much less efficient energy-wise. My crawl space is 2,700 square feet, but only about 4' high. So it is equivalent to about a 1500 sq ft garage with 8 ft ceilings. Most of these units consume 6-8 amps which means using a lot of electricity, so pay notice to it's efficiency and amp rating.
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#14
(02-20-2018, 04:37 AM)frule Wrote: Run your dehumidifier for 24 hours and collect the water. Then you will have a true reading of it's efficiency. Check your humidity at that point. I have a Sante Fe Advance 2 that is rated at 90 pints/24 hours and it easily meets that 90 pints. It keeps my encapsulated crawl space at 45% without running a lot. But it is a fairly large, high-end model ($1400).

I do not know how efficient it is, but I know it is not doing the job.  I added a second 30 pint unit and they both ran all day and are not catching up.  Eventually I will get the garage insulated and get some decent overhead doors installed.  That may help.  In the meantime I need to pick up a fairly good sized dehumidifier for the garage.  The two units I have work OK in the house in the summer time, one on each level.
I tried not believing.  That did not work, so now I just believe
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#15
This is part of what I do for our school district during the summer months when we turn off the A/C.  It is my job to mitigate mold potential via dehumidification in our school buildings.   How much water a dehumidifier will pull can vary.  What it pulls out today, may not be what it does tomorrow.  Variation in temperature, air infiltration, and ambient relative humidity affect the pull rate.  

Insulating is well and good, but stopping air infiltration is a lot more important.
 During the summer one area we shut down is our 12,000 sq.ft. carpeted high school media center.
We place two 40 pint dehumidifiers in there, drain to 65 gallon trash containers, close the doors, close the HVAC outside air dampers and let them run.  We log the relative humidity to check.  We empty the trash container about every two-three weeks.

The first couple of days they will pull their max, then a little less each day.  Within a week they are down to about a gallon or two a day.  The two of them easily keep the 12,000 sq. ft. media center with 14 ft ceilings at about 40% relative humidity.  

We put a dehumidifier in all of our classrooms that have carpeting.  We have a couple of wings in buildings where all the rooms are carpeted.  We seal the wing, open the classroom doors and put a commercial dehumidifier in the hallway(Fantech 250).  

The key is stopping air infiltration.  As long as you isolate the garage, even a smaller dehumidifier will eventually dry it out.
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#16
(02-20-2018, 09:54 PM)srv52761 Wrote: This is part of what I do for our school district during the summer months when we turn off the A/C.  It is my job to mitigate mold potential via dehumidification in our school buildings.   How much water a dehumidifier will pull can vary.  What it pulls out today, may not be what it does tomorrow.  Variation in temperature, air infiltration, and ambient relative humidity affect the pull rate.   

Insulating is well and good, but stopping air infiltration is a lot more important.
 During the summer one area we shut down is our 12,000 sq.ft. carpeted high school media center.
We place two 40 pint dehumidifiers in there, drain to 65 gallon trash containers, close the doors, close the HVAC outside air dampers and let them run.  We log the relative humidity to check.  We empty the trash container about every two-three weeks.

The first couple of days they will pull their max, then a little less each day.  Within a week they are down to about a gallon or two a day.  The two of them easily keep the 12,000 sq. ft. media center with 14 ft ceilings at about 40% relative humidity.  

We put a dehumidifier in all of our classrooms that have carpeting.  We have a couple of wings in buildings where all the rooms are carpeted.  We seal the wing, open the classroom doors and put a commercial dehumidifier in the hallway(Fantech 250).  

The key is stopping air infiltration.  As long as you isolate the garage, even a smaller dehumidifier will eventually dry it out.

Thanks.  That info is helpful!  I do know that I need to stop the air infiltration.  The insulating process will be more than putting in insulation.  That is why the doors are on the list.  I likely should do a thermal study also, to see where any other leaks are at.
I tried not believing.  That did not work, so now I just believe
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